Not applicable.
The present invention relates generally to agricultural equipment and more specifically to an extendable multi-stage hitch assembly for linking an agricultural implement to a prime mover.
Various types of agricultural implements have been developed that can be linked via an implement tongue member to a tractor hitch or other type of prime mover to facilitate different tasks including, for example, seeding, fertilizing and tilling. While there are many different factors that have to be considered when assessing the value of a particular implement, one relatively important factor is how quickly the implement can accomplish the task that the implement has been designed to facilitate. One way to increase task speed has been to increase implement width thereby reducing the number of passes required to perform the implement""s task for an entire field. Thus, for instance, doubling the width of a seeding implement generally reduces the time required to completely seed a field by half.
With the development of modern high-powered tractors and implements, many implements extend to operating field widths of 40 feet or more. Hereinafter when an implement is extended into an operating configurations to accomplished specific tasks (e.g., seeding, tilling, etc.), the implement will be said to be in an operating position and have an operating width.
Unfortunately, while expansive implement operating widths are advantageous for quickly accomplishing tasks, such expansive widths cannot be tolerated during implement transport and storage. With respect to transport, egresses to many fields are simply not large enough to accommodate transport of a 40 plus foot implement into and out of the fields. In addition, often buildings and fences obstruct passageways and therefore will not allow transport. Moreover, many farm fields are separated by several miles and farmers have to use commercial roadways to transport their implements to and from fields. Essentially all commercial roadways are not designed to facilitate wide implement transport.
Recognizing the need for expansive implement operating widths and relatively narrow transport widths, the industry has developed some solutions that facilitate both transport and operating widths. To this end, one solution has been to provide piece-meal implements that can be disassembled into separate sections and stacked on a wheel supported implement section or on a separate trailer for transport. Obviously this solution is disadvantageous as it requires excessive labor to assemble and disassemble the implements between transport and intended use and may also require additional equipment (e.g., an additional trailer).
Another solution has been to provide a folding implement configuration. For instance, in a xe2x80x9cscissors typexe2x80x9d configuration, where an implement chassis is supported by wheels, right and left implement bars are pivotally mounted to the chassis where each bar is moveable between an operating position extending laterally from the chassis and a transport position where the bar is forwardly swingable over the tongue member and supportable by the tongue member during transport. As another instance, xe2x80x9cpivotal-typexe2x80x9d configurations provide a single implement bar centrally mounted for pivotal movement on a wheel supported chassis where the single bar is pivotable about the mount so that half of the bar extends over the tongue member and is supportable thereby and the other half of the bar extends away from the tractor behind the chassis. In either of these scissors or pivotal configurations, the tongue member has to be long enough to accommodate half the implement bar length plus some clearance required to allow a tractor linked to the tongue member to turn left and right. Thus, for instance, where the implement operating width is 40 feet, the tongue member generally has to be greater than 20 feet long.
While task speed is one important criteria with which to judge implement value, one other important criteria is implement effectiveness and efficiency. In agricultural endeavors, perhaps the most important measure of effectiveness is yield per acre. For this reason, when seeding a field, a farmer wants to seed every possible square foot of the field and thereafter, when maintaining (i.e., tilling, fertilizing, etc.) and harvesting a field, the farmer wants to avoid destroying the plants in the field. To maximize field seeding, farmers typically travel along optimal field paths. For instance, to ensure that seed is planted along the entire edge of a field, a farmer typically starts seeding the field by first traveling around the edge of the field with a seeding implement at least once and often two or more times along adjacent consecutively smaller paths prior to traveling in parallel rows through the field. These field edge paths are generally referred to in the industry as headland passes. By performing one or more headland passes about a field edge prior to performing parallel passes, the farmer provides a space for turning the tractor and implement around between parallel passes while still covering the entire space along the field edge.
While headland passes increase overall field coverage, whenever a tractor is driven over field sections that have already been seeded, the tractor and implement wheels crush the seeds or growing plants that they pass over and therefore reduce overall field production (i.e., yield per acre). For this reason, as known in the industry, where possible, farmers routinely attempt to reduce the number of headland passes required in a field.
Unfortunately, the number of headland passes required to facilitate complete field coverage is related to the turning radius of a tractor and implement combination and the combination turning radius is directly related to the length of the tongue member between the implement and the tractor. Thus, for instance, where the tongue is six feet long the turning radius may require only one headland pass while a twenty foot long tongue may require two or more headland passes to facilitate complete coverage.
Recognizing that a short tongue during implement operation reduces the number of required headland passes and therefore increases efficiency and that a long tongue is desirable to accommodate pivotal and scissors type implement configurations, some industry members have developed staged tongue members that expand to accommodate implement transport and retract to provide a minimal turning radius during implement operation. One of these solutions provides a single stage telescoping tongue member including a first tongue member mounted to an implement chassis and a second tongue member that is telescopically received in the first tongue member. To facilitate expansion and retraction, a hydraulic cylinder is positioned within one of the first and second tongue members with a base member mounted to one of the tongue members and a rod secured to the other of the tongue members. With relatively large implements and tractors, the force required by the cylinder is relatively large. By placing the cylinder inside the tongue members, cylinder force is evenly distributed thereby reducing cylinder wear, reducing cylinder requirements and increasing the useful cylinder life cycle.
While better than non-telescoping tongue members, unfortunately, single stage members cannot telescope between optimal maximum and minimum lengths. For this reason, where single stage tongue members have been employed, either extended implement operating width has been minimized or extra headland passes have been used to accommodate a larger than optimum turning radius.
One other solution has been to provide a multi-stage tongue member that is able to telescope between optimal maximum and minimum lengths. Designing workable multi-stage tongue assemblies, however, has proven to be a difficult task. To this end, a separate cylinder is required for each stage in a multi-stage assembly. For instance, in a two stage assembly at least two cylinders are required. Unfortunately, in the case of a retracted multi-stage tongue assembly, the retracted assembly can only accommodate a single internally mounted cylinder (i.e., a cylinder mounted within the internal tongue assembly member). As indicated above, to balance cylinder load during operation and thereby minimize cylinder wear and increase useful cylinder lifecycle, the industry has opted to place tongue dedicated cylinders inside tongue member passageways and external tongue dedicated cylinders have not been considered a viable option.
One exemplary and seemingly workable multi-stage tongue assembly is described in U.S. Pat. No. 5,113,956 which is entitled xe2x80x9cForwardly Folding Tool Barxe2x80x9d and which issued on May 19, 1992 (hereinafter xe2x80x9cthe ""956 patentxe2x80x9d). The implement configuration in the ""956 patent teaches a scissors-type implement having left and right bar members mounted to a wheel supported chassis for pivotal rotation between an extended operating position and a transport position over the tongue assembly. The tongue assembly is mounted to the chassis and extends toward a tractor including several (e.g., 5) telescoped tongue members including a distal tongue member 14 that actually links to a tractor hitch. To move the bar members between the operating and transport positions the ""956 patent teaches that first and second hydraulic cylinders are mounted between the chassis and a point spaced from the chassis on each of the right and left bar members, respectively. By extending cylinder rods, the bar members are driven into extended operating positions and when the rods are retracted the bar members are driven into transport positions.
The ""956 patent teaches that the tongue assembly can be extended and retracted while the bar members are driven between their operating and transport positions and by the first and second hydraulic cylinders by attaching braces between the bar members and the distal tongue member. More specifically, a first rigid brace is pivotally secured at one end about midway along the right bar member and so as to form an acute angle therewith and at an opposite end to the distal tongue member and a second rigid brace is pivotally secured at one end about midway along the left bar member so as to form an acute angle therewith and at an opposite end to the distal tongue member. The ""956 patent teaches that when the cylinder rods are retracted so that the bar members are in the transport position, the tongue assembly is extended so that the distal end of the assembly clears the ends of the bar members. When the cylinder rods are extended, the bar members are driven toward their extended operating positions and the braces simultaneously pull the distal tongue member toward the chassis thereby causing the tongue assembly to retract. By reversing the rods so that the rods extend, the braces force the distal tongue member away from the chassis thereby causing the tongue assembly to extend. Thus, the ""956 patent configuration replaces the tongue dedicated rods with the first and second braces on opposite sides of the tongue assembly, the braces in effect operating as rods to extend and retract the tongue assembly and providing a balanced load to the distal tongue member during extension or retraction.
The ""956 solution, like other solutions, has several shortcomings. First, because the ""956 patent configuration cylinders are linked between the chassis and the bar members, in the case of some implements, the cylinders will get in the way of implement components (e.g., seeding buckets, ground engaging tools, etc.). Similarly, because of the locations of the braces (i.e., secured between central points of the braces and the distal tongue member), the braces also will obstruct use of certain implement components.
Second, in order to simultaneously drive the bar members between the operating and transport positions and drive the distal tongue member between the retracted and extended positions, the cylinders have to be relatively large and therefore expensive. One way to reduce cylinder size is to modify the implement configuration to increase the acute angles that the braces form with each of the bar members when the bar members are in the extended operating positions. This solution, however, leads to a third problem with the ""956 patent configuration. Specifically, to simultaneously provide a workable design including braces and accommodate larger acute angles that enable the use of smaller cylinders, the overall retracted tongue assembly length must be increased which is contrary to the primary purpose for which the assembly has been designed (i.e., to reduce tongue length during implement operation and increase tongue length during implement transportation).
In any extendable tongue assembly design, it is important to provide some mechanism to maintain the tongue assembly in the retracted position during implement operation and in the extended position during transport. In the case of configurations that rely on hydraulics to drive tongue members between extended and retracted positions, assuming the hydraulic system operates properly, the hose and cylinder pressures can generally be relied upon to maintain assembly positions. However, sometimes hydraulic systems fail and therefore, ideally, some backup locking system is provided.
Some assembly designs provide a manually operated mechanical locking mechanism to accomplish this task. For instance, to lock an assembly in an extended position, a farmer may be required to insert a locking pin through tongue member apertures that align when the assembly is retracted. Similar steps may also be used to lock the assembly in the extended position. Unfortunately, in the case of manual locking mechanisms, farmers may opt not to use the manual mechanisms and instead may simply rely upon the integrity of the hydraulic system.
Still other systems have been designed to include automatic locking mechanisms. For instance, referring again to the ""956 patent, the ""956 patent teaches a hydraulically operated latch locking mechanism that is mounted to the distal tongue member that engages a stop member that extends from the tongue member mounted to the chassis when the assembly is in the retracted position. When the assembly is in an extended position and the bar members are in a transport position, downward extending hooks at the distal ends of the bar members are positioned over receiving apertures such that, when implement support wheels are raised, if the hooks and apertures are properly aligned, the hooks are received in the apertures and lock the entire assembly, including the tongue members, in position for transport.
While better than a manual mechanism that may be ignored, the ""956 patent locking mechanism still has shortcomings. For instance, the latching mechanism relies on gravity to maintain the latch over the stop member while the implement is in the operating position. Where an implement is pulled through a field and hits a bump or a pot hole, the latch member may be jostled upward overcoming gravity and thereby becoming unlatched. Similarly, during transport the implement may be jostled thereby causing the hooks to lift out of the receiving apertures so that the assembly becomes unlocked.
In addition, the hook and aperture transport locking mechanism may not always operate well as alignment of the hooks and apertures is required for successful operation and therefore manufacturing and operating tolerances have to be relatively tight. This is especially true where movement from the operating to the transport positions has to be performed in an uneven field environment where similar hydraulic forces may drive the left and right hand bar members to different relative positions with respect to receiving apertures (i.e., after movement toward the transport positions the bar member hooks on the left and right bar members may be differently aligned with receiving apertures on the distal tongue member so that some type of manual adjustment is necessary).
Moreover, the ""956 patent requires separate mechanisms for locking the tongue assembly in each of the extended and retracted positions. As in the case of any apparatus, additional components typically translate into higher manufacturing and maintenance costs and therefore should be avoided whenever possible.
Therefore, a need exists for a simple and relatively inexpensive multistage tongue assembly that includes a simple and effective automatic locking mechanism which facilitates optimal maximum and minimum tongue lengths and which will not obstruct implement component use during implement operation.
It has been recognized that where separate hydraulic cylinders have been provided for each stage in a multi-stage tongue assembly, the cylinder loads are shared between the separate cylinders and therefore the overall load requirements of each stage cylinder are reduced appreciably. Where cylinder load is reduced the cylinder can be placed xe2x80x9coff-loadxe2x80x9d center without appreciably affecting load balance on the cylinder and therefore without appreciably reducing cylinder lifecycle. Thus, it has been recognized that, in the case of a multi-stage tongue assembly that can accommodate only a single internally mounted cylinder, additional externally mounted cylinders can be provided for each of the additional stages. For instance, in the case of a two stage assembly, a first stage may be motivated via an internally mounted cylinder and a second stage may be motivated by an externally mounted cylinder. In this case, the external cylinder will only assume a fraction (e.g., 50%) of the overall load and therefore can be placed off-load center without appreciable effects and without a balancing cylinder on the other side of the tongue assembly.
Thus, according to one embodiment of the invention, the invention includes a multi-stage tongue assembly including a separate hydraulic cylinder for each stage where at least one of the cylinders is mounted externally of the tongue members. For instance, in the case of a two stage assembly, one cylinder is mounted externally and the other cylinder may be mounted either internally or externally, in the case of a three stage assembly, at least two of the cylinders are mounted externally and the third cylinder may be mounted either internally or externally.
In addition, it has been recognized that a single simple locking mechanism can be used to lock telescoping tongue members corresponding to an assembly stage in each of extended and retracted positions. To this end, where a stage includes a first tongue member and a second tongue member that is receivable within the passageway formed by the first tongue member, the locking mechanism includes at least one latching member that is pivotally mounted to the first member and that extends past the end of the first member from which the second member telescopes. A distal end of the latch member extends toward the second member and a spring biases the distal end toward the second member. A hydraulic cylinder is mounted to the latch member such that, when the cylinder rod is extended, the rod overcomes the spring force and forces the distal end away from the second member. The second member forms at least first and second slots or apertures corresponding to the retracted and extended stage positions which are aligned with the distal end when the second member is in the retracted and extended positions, respectively. Thus, when the second member is in the retracted position and the cylinder is de-energized, the distal end is forced into and held within the first aperture by the spring. Upon energizing the latching cylinder the distal end is forced out of the first aperture and the tongue cylinders can be used to force the second member into the extended position. Once in the extended position, when the latching cylinder is de-energized, the spring forces the distal end toward the second member and into the second slot thereby locking the relative positions of the first and second cylinders. A separate locking mechanism is provided for each assembly stage.
Moreover, it has been recognized that adjustable stop members can be provided that allow for after manufacturing adjustment of the relative positions of the stop members and locking mechanism components to ensure that locking mechanism components can be properly and automatically aligned thereby reducing required manufacturing tolerances and thus reducing manufacturing costs.
Consistent with the above, the present invention includes an extendable apparatus for securing an agricultural implement to a hitch receiving member of a vehicle, the apparatus comprising a first elongated tongue member having a first external surface and forming a first passageway, a second elongated tongue member having a second external surface, forming a second passageway and slidably mounted within the first passageway, the first and second tongue members being a first tongue pair, a third elongated tongue member having a third external surface, forming a third passageway and slidably mounted within the second passageway, the second and third tongue members being a second tongue pair, one of the first and third tongue members mounted to the implement, a first tongue cylinder including a first rod member mounted within a first base member and having a first distal end, the first base member and first distal end secured to separate ones of the first tongue pair members such that when the first rod member is extended the second tongue member extends from the first passageway and when the first rod member is retracted the second tongue member is substantially received within the first passageway and a second tongue cylinder including a second rod member mounted within a second base member and having a second distal end, the second base member and second distal end secured to separate ones of the second tongue pair members such that when the second rod member is extended the third tongue member extends from the second passageway and when the second rod member is retracted the third tongue member is substantially received within the second passageway wherein at least one of the first and second cylinders is secured to the external surfaces of a tongue pair.
In one embodiment the first base member and the first distal end are secured to the external surfaces of the first tongue pair. More specifically, the first base member may be secured to the external surface of the first tongue member and the first distal end may be secured to the external surface of the second tongue member. Here, each of the first and second tongue members may have first and second ends and, when the second tongue member is substantially received within the first passageway, the first end of the second tongue member may be proximate the first end of the first tongue member and when the second tongue member is extended from the first passageway, the first end of the second tongue member may be proximate the second end of the first tongue member, the first distal end secured to the second tongue member proximate the second end of the second tongue member. The second tongue cylinder may be mounted inside the third passageway.
Furthermore, in some embodiments each of the second and third tongue members has first and second ends and, when the third tongue member is substantially received within the second passageway, the first end of the third tongue member is proximate the first end of the second tongue member and when the third tongue member is extended from the second passageway, the first end of the third tongue member is proximate the second end of the second tongue member, the second distal end secured to the second tongue member proximate the first end of the second tongue member.
In some embodiments the second tongue cylinder is mounted inside one of the first and third passageways. Furthermore, each of the second and third tongue members may have first and second ends and, when the third tongue member is substantially received within the second passageway, the first end of the third tongue member may be proximate the first end of the second tongue member and when the third tongue member is extended from the second passageway, the first end of the third tongue member may be proximate the second end of the second tongue member, the second distal end secured to the second tongue member proximate the first end of the second tongue member.
In yet other embodiments the tongue members together form a tongue assembly having an external assembly surface and each of the first and second tongue cylinders is secured to the assembly surface. Here, the first tongue cylinder may be secured to a first side of the assembly surface and the second tongue cylinder may be secured to a second side of the assembly surface and wherein the second side is different than the first side.
Some embodiments further include at least a fourth elongated tongue member having a fourth external surface, forming a fourth passageway and slidably mounted within the third passageway, the third and fourth tongue members being a third tongue pair, the apparatus further including a third tongue cylinder including a third rod member mounted within a third base member and having a third distal end, the third base member and third distal end secured to separate ones of the third tongue pair members such that when the third rod member is extended the fourth tongue member extends from the third passageway and when the third rod member is retracted the fourth tongue member is substantially received within the third passageway and, wherein, the tongue members together form a tongue assembly having an external assembly surface and wherein at least two of the tongue cylinders are secured to the assembly surface, a first of the at least two cylinders secured to a first side of the assembly surface and a second of the at least two cylinders secured to a second side of the assembly surface and wherein the second side is different than the first side.
In most embodiments the first and second tongue cylinders are plumbed in parallel.
In another aspect the invention further includes a first locking assembly mounted to one of the first tongue pair members and operable to lock the first tongue pair members in at least one of a retracted and an extended position and also including a second locking assembly mounted to one of the second tongue pair members and operable to lock the second tongue pair members in at least one of a retracted and an extended position. Here the first locking assembly may be operable to lock the first tongue pair members in each of the extended and retracted positions and the second locking assembly may be operable to lock the second tongue pair members in each of the extended and retracted positions.
More specifically, each of the first and second tongue members may have first and second ends and wherein, when the second tongue member is in the retracted position, the first end of the second tongue member is proximate the first end of the first tongue member and when the second tongue member is in the extended position, the first end of the second tongue member may be proximate the second end of the first tongue member, the first locking assembly including at least a first arm member, a first spring member and a first locking cylinder, the first arm member pivotally mounted to the external surface of the first tongue member and having a first locking end that extends past the second end of the first tongue member and toward the second tongue member, the spring member secured proximate the first locking end to pull the first locking end toward the second tongue member, the first locking cylinder secured proximate the first locking end such that when a first locking cylinder rod is extended, the first locking end is forced away from the second tongue member, the second tongue member forming first and second slots proximate the first and second ends of the second tongue member, respectively, for receiving the first locking end when the second tongue member is in the retracted and extended positions, respectively.
The first locking assembly may further include a second arm member pivotally mounted to the external surface of the first tongue member on a side of the first tongue member opposite the first arm member and having a second locking end that extends past the second end of the first tongue member and toward the second tongue member, the spring member further secured proximate the second locking end to pull the second locking end toward the second tongue member, the first locking cylinder further secured proximate the second locking end such that when the first locking cylinder rod is extended, the second locking end is forced away from the second tongue member, the second tongue member forming third and fourth slots proximate the first and second ends of the second tongue member, respectively, for receiving the second locking end when the second tongue member is in the retracted and extended positions, respectively.
Each of the second and third tongue members may have first and second ends and, when the third tongue member is in the retracted position, the first end of the third tongue member may be proximate the first end of the second tongue member and when the third tongue member is in the extended position, the first end of the third tongue member may be proximate the second end of the second tongue member. Here, the second locking assembly may include third and fourth arm members, a second spring member and a second locking cylinder, the third and fourth arm members pivotally mounted to opposite sides of the external surface of the second tongue member and having third and fourth locking ends that extend past the second end of the second tongue member and toward the third tongue member, respectively, the second spring member secured proximate the third and fourth locking end to pull the third and fourth locking ends toward the third tongue member, the second locking cylinder secured proximate the third and fourth locking ends such that when a second locking cylinder rod is extended, the third and fourth locking ends are forced away from the third tongue member, the third tongue member forming fourth and fifth slots proximate the first and second ends of the third tongue member, respectively, for receiving the third locking end when the third tongue member is in the retracted and extended positions, respectively, and also forming sixth and seventh slots proximate the first and second ends of the third tongue member, respectively, for receiving the forth locking end when the third tongue member is in the retracted and extended positions, respectively.
Here, the locking cylinders may be plumbed in parallel with the first and second tongue cylinders.
The invention further includes an extendable apparatus for securing an agricultural implement to a hitch receiving member of a vehicle, the apparatus comprising a first elongated tongue member having a first external surface and first and second ends, forming a first passageway and mounted to the implement, a second elongated tongue member having a second external surface and first and second ends, forming a second passageway and slidably mounted within the first passageway for movement between a retracted position where the first end of the second tongue member is proximate the first end of the first tongue member and an extended position wherein the first end of the second tongue member is proximate the second end of the first tongue member, a locking assembly including at least a first arm member, a first spring member and a first locking cylinder, the first arm member pivotally mounted to the external surface of the first tongue member and having a first locking end that extends past the second end of the first tongue member and toward the second tongue member, the spring member secured proximate the first locking end to pull the first locking end toward the second tongue member, the first locking cylinder secured proximate the first locking end such that when a first locking cylinder rod is extended, the first locking end is forced away from the second tongue member, the second tongue member forming first and second slots proximate the first and second ends of the second tongue member, respectively, for receiving the first locking end when the second tongue member is in the retracted and extended positions, respectively.
In some embodiments the first locking assembly further includes a second arm member pivotally mounted to the external surface of the first tongue member on a side of the first tongue member opposite the first arm member and having a second locking end that extends past the second end of the first tongue member and toward the second tongue member, the spring member further secured proximate the second locking end to pull the second locking end toward the second tongue member, the first locking cylinder further secured proximate the second locking end such that when the first locking cylinder rod is extended, the second locking end is forced away from the second tongue member, the second tongue member forming third and fourth slots proximate the first and second ends of the second tongue member, respectively, for receiving the second locking end when the second tongue member is in the retracted and extended positions, respectively.
In other embodiments the first and second tongue members are a first tongue pair and the locking mechanism is a first locking assembly, the apparatus further including a third elongated tongue member having a third external surface and first and second ends, forming a third passageway and slidably mounted within the second passageway for movement between a retracted position where the first end of the third tongue member is proximate the first end of the second tongue member and an extended position wherein the first end of the third tongue member is proximate the second end of the second tongue member, the second and third tongue members being a second tongue pair and a second locking assembly including third and fourth arm members, a second spring member and a second locking cylinder, the third and fourth arm members pivotally mounted on opposite sides of the external surface of the second tongue member and having third and fourth locking ends that extends past the second end of the second tongue member and toward the third tongue member, the second spring member secured proximate the third and fourth locking ends to pull the third and fourth locking ends toward the third tongue member, the second locking cylinder secured proximate the third and fourth locking ends such that when a second locking cylinder rod is extended, the third and fourth locking ends are forced away from the third tongue member, the third tongue member forming fifth and sixth slots proximate the first and second ends of the third tongue member, respectively, for receiving the third locking end when the third tongue member is in the retracted and extended positions, respectively, the third tongue member also forming seventh and eighth slots proximate the first and second ends of the third tongue member, respectively, for receiving the fourth locking end when the third tongue member is in the retracted and extended positions, respectively.
Moreover, the invention also includes an extendable apparatus for securing an agricultural implement to a hitch receiving member of a vehicle, the apparatus comprising a first elongated tongue member having a first external surface and first and second ends, forming a first passageway and mounted to the implement, a second elongated tongue member having a second external surface and first and second ends, forming a second passageway and slidably mounted within the first passageway for movement between a retracted position where the first end of the second tongue member is proximate the first end of the first tongue member and an extended position wherein the first end of the second tongue member is proximate the second end of the first tongue member, the first and second tongue members being a first tongue pair, a third elongated tongue member having a third external surface and first and second ends, forming a third passageway and slidably mounted within the second passageway for movement between a retracted position where the first end of the third tongue member is proximate the first end of the second tongue member and an extended position wherein the first end of the third tongue member is proximate the second end of the second tongue member, the second and third tongue members being a second tongue pair, a first locking assembly mounted to one of the first tongue pair members and operable to lock the first tongue pair members in each of a retracted and an extended position and a second locking assembly mounted to one of the second tongue pair members and operable to lock the second tongue pair members in each of a retracted and an extended position.
In other embodiments the first locking assembly includes first and second arm members, a first spring member and a first locking cylinder, the first and second arm members pivotally mounted on opposite sides of the external surface of the first tongue member and having first and second locking ends that extends past the second end of the first tongue member and toward the second tongue member, the first spring member secured proximate the first and second locking ends to pull the first and second locking ends toward the second tongue member, the first locking cylinder secured proximate the first and second locking ends such that when a first locking cylinder rod is extended, the first and second locking ends are forced away from the second tongue member, the second tongue member forming first and second slots proximate the first and second ends of the second tongue member, respectively, for receiving the first locking end when the second tongue member is in the retracted and extended positions, respectively, the second tongue member also forming third and fourth slots proximate the first and second ends of the second tongue member, respectively, for receiving the second locking end when the second tongue member is in the retracted and extended positions, respectively, and the second locking assembly includes third and fourth arm members, a second spring member and a second locking cylinder, the third and fourth arm members pivotally mounted on opposite sides of the external surface of the second tongue member and having third and fourth locking ends that extends past the second end of the second tongue member and toward the third tongue member, the second spring member secured proximate the third and fourth locking ends to pull the third and fourth locking ends toward the third tongue member, the second locking cylinder secured proximate the third and fourth locking ends such that when a second locking cylinder rod is extended, the third and fourth locking ends are forced away from the third tongue member, the third tongue member forming fifth and sixth slots proximate the first and second ends of the third tongue member, respectively, for receiving the third locking end when the third tongue member is in the retracted and extended positions, respectively, the third tongue member also forming seventh and eighth slots proximate the first and second ends of the third tongue member, respectively, for receiving the fourth locking end when the third tongue member is in the retracted and extended positions, respectively.
Still other embodiments include first and second tongue cylinders, the first tongue cylinder mounted to the first tongue pair to drive the first pair members between the extended and retracted positions and the second tongue cylinder mounted to the second tongue pair to drive the second pair members between the extended and retracted positions.